An engineering expert has confirmed New Zealand's bridges are still safe to use after the collapse of a large bridge in Italy.
The Morandi bridge in Genoa collapsed on Tuesday evening and the current death toll from the disaster stands at 39.
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New Zealand has its own fraught history with bridge safety, none have collapsed causing mass casualties, but there have been engineering reports that caused concern.
A 2007 report from engineering firm Beca found the iconic Harbour Bridge clip-ons were at risk of immediate, catastrophic failure in certain circumstances, such as a traffic jam trapping a lot of heavy trucks on the bridge.
It was later reinforced using 920 tonnes of reinforcing material.
Further back in 1904 the precursor to central city Grafton Bridge was closed after a report found it was damaged beyond repair and the city was lucky that it had not collapsed yet.
The bridge was demolished and rebuilt at a cost of £33,000 or the equivalent of $1.3 million in 2018. It was closed for 15 months in 2008 to allow for seismic strengthening.
Canterbury University professor Alessandro Palermo told RadioLIVE's Morning Talk New Zealand has a far more strict inspection scheme than Italy and the chances of a bridge collapse happening here are remote.
"The NZTA, they have a quite rigorous maintenance programme and bridges in New Zealand are quite well inspected," he said.
"They have general inspections every two years, and then they have a more detailed inspection after six years. That also depends on the condition of the bridge [and] where the bridge is located."
It's also important to note the bridge in Italy was a particular kind of structure and had few fail safes built into it.
"So the bridge that collapsed in Genoa is a bridge that doesn't have a lot of redundancy, that means that if something goes wrong with one element, the bridge collapsed," Professor Palermo said.
"Other types of bridges have a redundancy, which means that the load path will be changed and means that yes, there is something wrong, but that doesn't mean that we'll have a total collapse of the bridge."
Bridge lifespans could be a concern, but Professor Palermo said the 2000-year-old Roman aqueducts are still standing, long after they were past their use-by.
"When bridges were designed, let's say 50,60 years ago, they were designed with a life span of 50 years, now we're designing with 100 years," he said.
"But that doesn't mean that the bridge at year 51 collapses."
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